Semiconductor Microcooler

ABSTRACT

A semiconductor microcooler is fabricated by forming fins in a semiconductor substrate and forming a metal layer upon the fins. A stacked microcooler may be formed by stacking a plurality of semiconductor microcoolers. The microcoolers may be positioned such that the fins of each microcooler are vertically aligned. The microcoolers may include an inlet passage to accept coolant and an outlet passage to expel the coolant. One or more microcoolers may be thermally connected to an electronic device heat generating device, such as an integrated circuit (IC) chip, or the like. Heat from the electronic device heat generating device may transfer to the one or more microcoolers. A flow of cooled liquid may be introduced through the passages and heat from the one or more microcoolers may transfer to the liquid coolant.

FIELD OF THE EMBODIMENTS

Embodiments of the present invention generally relate to coolingelectronic devices, such as integrated circuit (IC) chips, processors,or the like, with a liquid cooling system that utilizes one or moresemiconductor microcoolers.

DESCRIPTION OF THE RELATED ART

Though the size constraints of electronic devices are generallydecreasing, the computing power of those devices are generallyincreasing. As such, electronic systems will generally require highpower consumption devices which requires the removal of an increasedamount of heat. Another approach may be to package more computingdevices in a smaller area which would also require the removal of anincreased amount of heat.

SUMMARY

In an embodiment of the present invention, a method is presented. Themethod includes forming a first semiconductor microcooler by removingportions of a first bulk silicon substrate to form a plurality of firstsilicon fins and a plurality of first fin trenches forming a firstcopper layer upon sidewalls of each of the plurality of first siliconfins, by forming a first bonding layer upon a respective upper surfaceof each of the first plurality of silicon fins, and by forming a firstaccess passage within the first semiconductor microcooler by removing aportion of a first silicon fin and a portion of the bulk siliconsubstrate adjacent to the portion of the first silicon fin. Each firstfin trench separates adjacent first silicon fins. The method furtherincludes forming a second semiconductor microcooler by removing portionsof a second bulk silicon substrate to form a plurality of second siliconfins and a plurality of second fin trenches, forming a second copperlayer upon sidewalls of each of the plurality of second silicon fins,and by forming a second bonding layer upon a respective upper surface ofeach of the second plurality of silicon fins. Each second fin trenchseparates adjacent second silicon fins. The method further includesstacking the first microcooler and the second microcooler by aligningthe plurality of first fin trenches with the plurality of second fintrenches and thermally connecting the first bonding layer and the secondbonding layer. The first access passage allows coolant within one ormore first fin trenches to pass through the first semiconductormicrocooler to one or more second fin trenches of the secondsemiconductor microcooler.

In another embodiment of the present invention, a heat transfer methodis presented. The method includes causing a flow of liquid coolantthrough a plurality of fin trenches of a stacked semiconductormicrocooler. The stacked semiconductor microcooler includes a firstsemiconductor microcooler comprising a plurality of first silicon finsand a plurality of first fin trenches, a first copper layer uponsidewalls of each of the plurality of first silicon fins, a firstbonding layer upon a respective upper surface of each of the firstplurality of silicon fins, and a first access passage within the firstsemiconductor microcooler. Each first fin trench separates adjacentfirst silicon fins. The stacked semiconductor microcooler includes asecond semiconductor microcooler comprising a plurality of secondsilicon fins and a plurality of second fin trenches, a second copperlayer upon sidewalls of each of the plurality of second silicon fins,and a second bonding layer upon a respective upper surface of each ofthe second plurality of silicon fins. Each second fin trench separatesadjacent second silicon fins. The first access passage allows coolantwithin one or more first fin trenches to pass through the firstsemiconductor microcooler to one or more second fin trenches of thesecond semiconductor microcooler.

In another embodiment of the present invention, an electronic systemincludes: a stacked semiconductor microcooler and an integrated circuit(IC) chip. The stacked semiconductor microcooler includes a firstsemiconductor microcooler comprising a plurality of first silicon finsand a plurality of first fin trenches, a first copper layer uponsidewalls of each of the plurality of first silicon fins, a firstbonding layer upon a respective upper surface of each of the firstplurality of silicon fins, and a first access passage within the firstsemiconductor microcooler. Each first fin trench separates adjacentfirst silicon fins. The stacked semiconductor microcooler includes asecond semiconductor microcooler comprising a plurality of secondsilicon fins and a plurality of second fin trenches, a second copperlayer upon sidewalls of each of the plurality of second silicon fins,and a second bonding layer upon a respective upper surface of each ofthe second plurality of silicon fins. Each second fin trench separatesadjacent second silicon fins. The first access passage allows coolantwithin one or more first fin trenches to pass through the firstsemiconductor microcooler to one or more second fin trenches of thesecond semiconductor microcooler. The IC chip is thermally connected tothe second semiconductor microcooler.

These and other embodiments, features, aspects, and advantages willbecome better understood with reference to the following description,appended claims, and accompanying drawings.

BRIEF DESCRIPTION OF THE FIGURES

So that the manner in which the above recited features of the presentinvention are attained and can be understood in detail, a moreparticular description of the invention, briefly summarized above, maybe had by reference to the embodiments thereof which are illustrated inthe appended drawings.

It is to be noted, however, that the appended drawings illustrate onlytypical embodiments of this invention and are therefore not to beconsidered limiting of its scope, for the invention may admit to otherequally effective embodiments.

FIG. 1 depicts a prior art electronic system that utilizes a passivecooling system.

FIG. 2A and FIG. 2B depicts an IC chip package that is cooled by aliquid cooling system that utilizes one or more embodiments of thepresent invention.

FIG. 3 depicts a cross section view of a semiconductor microcooler,according to one or more embodiments of the present invention.

FIG. 4A, FIG. 4B, and FIG. 4C depicts a top view of a semiconductormicrocooler, according to one or more embodiments of the presentinvention.

FIG. 5 depicts a cross section view of a stacked semiconductormicrocooler, according to one or more embodiments of the presentinvention.

FIG. 6A depicts a cross section view of a semiconductor microcooler,according to one or more embodiments of the present invention.

FIG. 6B depicts a cross section view of a stacked semiconductormicrocooler, according to one or more embodiments of the presentinvention.

FIG. 7 depicts a cross section view of a stacked semiconductormicrocooler, according to one or more embodiments of the presentinvention.

FIG. 8 depicts an initial fabrication stage of a process flow to form asemiconductor microcooler, according to one or more embodiments of thepresent invention.

FIG. 9 depicts another fabrication stage of the process flow to form asemiconductor microcooler, according to one or more embodiments of thepresent invention.

FIG. 10 depicts another fabrication stage of the process flow to form asemiconductor microcooler, according to one or more embodiments of thepresent invention.

FIG. 11 depicts another fabrication stage of the process flow to form asemiconductor microcooler, according to one or more embodiments of thepresent invention.

FIG. 12 depicts another fabrication stage of the process flow to form asemiconductor microcooler, according to one or more embodiments of thepresent invention.

FIG. 13 depicts another fabrication stage of the process flow to form asemiconductor microcooler, according to one or more embodiments of thepresent invention.

FIG. 14 depicts another fabrication stage of the process flow to form asemiconductor microcooler, according to one or more embodiments of thepresent invention.

FIG. 15 depicts another fabrication stage of the process flow to form asemiconductor microcooler, according to one or more embodiments of thepresent invention.

FIG. 16 depicts another fabrication stage of the process flow to form asemiconductor microcooler, according to one or more embodiments of thepresent invention.

FIG. 17 depicts another fabrication stage of the process flow to form asemiconductor microcooler, according to one or more embodiments of thepresent invention.

FIG. 18 depicts an electronic system comprising an IC chip that iscooled by a liquid cooling system that utilizes one or more embodimentsof the present invention.

FIG. 19 depicts an electronic system comprising an IC chip that iscooled by a liquid cooling system that utilizes one or more embodimentsof the present invention.

FIG. 20 depicts a method for fabricating a semiconductor microcooler,according to one or more embodiments of the present invention.

FIG. 21 depicts a method for fabricating a semiconductor microcooler,according to one or more embodiments of the present invention.

FIG. 22, FIG. 23, and FIG. 24 depict a stacked semiconductormicrocooler, according to one or more embodiments of the presentinvention.

FIG. 25 and FIG. 26 depicts stacked semiconductor microcooler assembly,according to one or more embodiments of the present invention.

FIG. 27 depicts an electronic system comprising an IC chip that iscooled by a liquid cooling system that utilizes one or more embodimentsof the present invention.

DETAILED DESCRIPTION

A semiconductor microcooler is fabricated by forming fins in asemiconductor substrate and forming a metal layer upon the fins. Astacked microcooler may be formed by stacking a plurality ofsemiconductor microcoolers. The microcoolers may be positioned such thatthe fins of each microcooler are vertically aligned. The microcoolersmay include an inlet passage to accept coolant and an outlet passage toexpel the coolant. One or more microcoolers may be thermally connectedto an electronic device heat generating device, such as an integratedcircuit (IC) chip, or the like. Heat from the electronic device heatgenerating device may transfer to the one or more microcoolers. A flowof cooled liquid may be introduced through the passages and heat fromthe one or more microcoolers may transfer to the liquid coolant.

FIG. 1 depicts a prior art electronic device 100 utilizing a passivelycooled package 124. Electronic device 100 may be for example a computer,server, mobile device, tablet, and the like. Package 124 includes chip102, carrier 108, interconnects 122, underfill 110, thermal interfacematerial 112, lid 116, and adhesive 120. Chip 102 may be an IC chip,semiconductor die, processor, microchip, field programmable gate array,or the like. Carrier 108 may be an organic carrier or a ceramic carrierand provides mechanical support for chip 102 and electrical paths fromthe upper surface of carrier 108 to the opposing side of carrier 108.Interconnects 122 electrically connect chip 102 and the upper side ofcarrier 108 and may be a wire bond, solder bond, stud, conductive ball,conductive button, and the like. Underfill 110 may beelectrically-insulating, may substantially surround interconnects 122,may isolate individual interconnects 122, and may provide mechanicalsupport between chip 102 and carrier 108. Underfill 110 may also preventdamage to individual interconnects 122 due to thermal expansionmismatches between chip 102 and carrier 108.

When chip 102 is seated upon carrier 108, a reflow process may beperformed to join interconnects 122 to electrical contacts of both chip122 and carrier 108. After chip 102 is seated to carrier 108 a lid 116is attached to carrier 108 with adhesive 120 to cover chip 102.Generally, during operation of electronic device 100, heat needs to beremoved from chip 102. In this situation, lid 116 is both a cover and aconduit for heat transfer. As such, a thermal interface material 112 maythermally join lid 116 and chip 102.

Package 124 may be connected to a motherboard 106 via interconnects 114.Motherboard 106 may be the main printed circuit board of electronicdevice 100 and includes electronic components, such as a graphicsprocessing unit, memory, and the like, and provides connectors for otherperipherals. Interconnects 114 electrically connect the lower side ofcarrier 108 to motherboard 106 and may be a wire bond, solder bond,stud, conductive ball, conductive button, and the like. Interconnects114 may be larger and thus more robust than interconnects 122. Whenpackage 124 is seated upon motherboard 106 a second reflow process maybe performed to join interconnects 114 to electrical contacts of bothcarrier 108 and motherboard 106. Alternately, a mechanical pressurizedinterconnect via an intervening socket may be established.

To assist in the removal of heat from chip 102 a heat sink 104 may bethermally joined to package 124 via thermal interface material 118. Heatsink 104 is a passive heat exchanger that cools chip 102 by dissipatingheat into the surrounding air. As such, during operation of electronicdevice 100, a thermal path exists from chip 102 to heat sink 104 throughthermal interface material 112, lid 116, and thermal interface material118, and the like. Heat sink 104 may be connected to motherboard 106 viaone or more connection device 130. Connection device 130 may include athreaded fastener 132, standoff 134, backside stiffener 136, andfastener 138. Threaded fastener 132 may extend through heat sink 104,standoff 134, and backside stiffener 136 and provides compressive forcebetween heat sink 104 and backside stiffener 136. The length of standoff134 may be selected to limit the pressure exerted upon package 124 byheat sink 104 created by the compressive forces. Backside stiffener 136may mechanically support the compressive forces by distributing theforces across a larger area of motherboard 104. In other applications,connection device 130 may be a clamp, non-influencing fastener, cam, andthe like, system that adequately forces heat sink 104 upon package 124.

FIG. 2A and FIG. 2B depicts an IC chip package 200 that is cooled by aliquid cooling system. FIG. 2B is a cross section view of package 200 atthe AA plane as indicated in FIG. 2A. Package 200 includes IC chip 102,carrier 108, interconnects 122, underfill 110, thermal interfacematerial 112, a first housing 202, and second housing 204. First housing202, which may be referred herein as lower housing, may contact carrier108 and is thermally connected to IC chip 102 by way of thermalinterface material 112 which reduces air gaps between the IC chip 102and the lower housing 202. The term “thermally connected,” is hereindefined to be an indirect or direct connection between elements suchthat heat from one element transfers to the other element by thermalconduction more efficiently than if air separates the elements. Lowerhousing 202 may include an underside cavity 216 to allow for the IC chip102 to thermally connect with an IC chip facing surface of the cavity216 while a carrier facing surface of the housing 202 may simultaneouslythermally connect with carrier 108.

The second housing 202 may be sealed against, and is thermally connectedto, the first housing such that an air tight internal void or cavity 205is formed therebetween. The second housing 204 may include one or moreliquid coolant inlets 206 and one or more liquid coolant outlets 108. Aheat exchanger may cool the liquid coolant prior to being introducedinto the cavity 205. A flow 210 of liquid coolant may be induced by apump, or the like, from the heat exchanger to the one or more liquidcoolant inlets 206 through the cavity 205 and exiting the cavity 205 byway of the one or more liquid coolant outlets 108 whereby the liquidcoolant returns to the heat exchanger. As IC chip 102 generates heat,that heat is transferred into the housing 202 and into the liquidcoolant flowing through cavity 205. The heat exchanger, in turn, coolsthe liquid coolant prior to the liquid coolant being reintroduced intocavity 205. As such, cooled liquid coolant enters cavity 205 by the oneor more inlets 206 and heated liquid coolant exits cavity 205 by the oneor more outlets 108.

Cavity 205 may include a coolant flow 210 conduit region 212 thatdefines the coolant flow 210 in the general direction between theinlet(s) 206 and the outlet(s) 108. The region 212 is bounded by a frontplane(s) just downstream of the inlet(s) 206, by a rear plant justupstream of the outlet(s) 108, by an upper surface 207 of cavity 205, bya lower surface 203 of cavity 203, by a first side surface 209 of cavity205, and by a second side surface 211 of cavity 205.

FIG. 3 depicts a cross section view of a semiconductor microcooler 300,according to one or more embodiments of the present invention.Semiconductor microcooler 300 includes a plurality of semiconductor fins302 separated from neighboring fin(s) by respective fin trenches. Thefins 302 have a metal layer 304 thereupon. For example, the metal layer304 is formed on the upper surface of the fins, the front surface of thefins, the rear surface of the fins, a first side surface of the fins,and an opposing second side surface of the fins. The metal layer 304 mayalso be formed upon the lower surface of each fin trench. The first sidesurface of the fins 302 and the opposing second side surface of the fins302 may be parallel or may be angled relative thereto. For example, theshape of fins 302 may be generally rectangular or may be triangular.Further fin 302 cross section shapes that are contemplated are diamond,trapezoid, or the like. Semiconductor microcooler 300 may include alower surface 301, and upper surface 303, a first side surface 305, anda second side surface 307. In an embodiment, semiconductor fins 302 aresilicon fins and metal layer 304 is a copper layer.

The fins 302 may have a height of 0.5-5 mm and may have a width of25-1000 um.

One or more semiconductor microcooler(s) 300 may be thermally connectedto one or more surfaces of first housing 202 and/or the second housing204 that defines conduit region 212, to increase the surface areathereof. As such, heat from the one or more surfaces of first housing202 and/or the second housing 204 is transferred into the fins 302 andinto the metal layer 304. The semiconductor microcooler(s) 300 may bepositioned such that the fins 302 are generally parallel to thedirection of the liquid coolant flow 210. Generally, when semiconductormicrocooler(s) 300 are thermally connected to the one or more surfacesof first housing 202 and/or the second housing 204, the liquid coolantflows within the fin trenches. In this way, with the addition of the oneor more semiconductor microcooler(s) 300 within the conduit region 212,heat is transferred relatively more efficiently from the first housing202 and/or the second housing 204 into the liquid coolant flow 210.

FIG. 4A, FIG. 4B, and FIG. 4C depicts exemplary top views ofsemiconductor microcooler 300, according to one or more embodiments ofthe present invention. As depicted in FIG. 4A, fins 302 may be have arectangular top view shape and may extend from a front of thesemiconductor substrate to the rear of the semiconductor substrate. Asdepicted in FIG. 4B, fins 302 may be arranged in an array of row andcolumns of rectangular top view shaped fins, square top view shapedfins, or the like. As depicted in FIG. 4C, fins 302 may be arranged in astaggered array of rectangular top view shaped fins, square top viewshaped fins, or the like.

FIG. 5 depicts a cross section view of a stacked semiconductormicrocooler 300B, according to one or more embodiments of the presentinvention. Stacked semiconductor microcooler 300B includes a pluralityof stacked semiconductor microcooler 300. For example, stackedsemiconductor microcooler 300B includes a semiconductor microcooler 300₁, semiconductor microcooler 300 ₂, and semiconductor microcooler 300 ₃.Semiconductor microcooler 300 ₂ is stacked upon semiconductormicrocooler 300 ₁. Semiconductor microcooler 300 ₃ is stacked uponsemiconductor microcooler 300 ₂. For clarity, though three semiconductormicrocoolers 300 are shown stacked, a stacked semiconductor microcoolermay include two or more semiconductor microcoolers 300 stacked relativeeach other.

The plurality of stacked semiconductor microcooler 300 may have the sameorientation, as is depicted, whereby each lower surface 301 of eachsemiconductor microcooler 300 is facing the same direction. In suchimplementation, the top surface 303 of a semiconductor microcooler 300may be bonded and thermally connected to the lower surface 301 ofanother semiconductor microcooler 300. The semiconductor microcooler 300s may be stacked such that the fins 302 and fin trenches of thesemiconductor microcoolers 300 are aligned. First side surface 325 maybe formed by coplanar first side surfaces 305 of each semiconductormicrocooler 300. Likewise, second side surface 327 may be formed bycoplanar second side surfaces 307 of each semiconductor microcooler 300.

Alternatively, the plurality of stacked semiconductor microcooler 300may have differing orientation whereby lower surfaces 301 of two or moresemiconductor microcooler 300 may face towards each other or away fromeach other. In such implementation, the top surface 303 of asemiconductor microcooler 300 may be bonded and thermally connected tothe top surface 303 of another semiconductor microcooler 300. The fins302 and fin trenches of these semiconductor microcoolers 300 may bealigned, thereby increasing (e.g. doubling, etc.) the size of the fintrenches that separate the fins 302. First side surface 325 may beformed by a coplanar first side surface 305 of a first microcooler 300and a second side surface 307 of a second microcooler 300. Likewise,second side surface 327 may be formed by a coplanar second side surface307 of the first microcooler and the first side surface 307 of thesecond microcooler 300.

Stacked semiconductor microcooler 300B may include a lower surface 321,an upper surface 323, a first side surface 325, and a second sidesurface 325. Such surfaces 321, 323, 325, and/or 325 may be thermallyconnected to one or more surfaces of first housing 202 and/or the secondhousing 204 that defines conduit region 212, to increase the surfacearea thereof. As such, heat from the one or more surfaces of firsthousing 202 and/or the second housing 204 is transferred into the fins302 and into the metal layer 304. The stacked semiconductormicrocooler(s) 300B may be positioned such that the fins 302 of eachmicrocooler 300 are generally parallel to the direction of the liquidcoolant flow 210. Generally, when stacked semiconductor microcooler(s)300B are thermally connected to the one or more surfaces of firsthousing 202 and/or the second housing 204, the liquid coolant flowswithin the fin trenches. In this way, with the addition of the one ormore stacked semiconductor microcooler(s) 300B within the conduit region212, heat is transferred relatively more efficiently from the firsthousing 202 and/or the second housing 204 into the liquid coolant flow210.

FIG. 6A depicts a cross section view of a semiconductor microcooler300C, according to one or more embodiments of the present invention.Semiconductor microcooler 300C includes a plurality of semiconductorfins 302 that are each separated from an immediate neighboring fin by afin trench. The fins 302 have a bonding layer 310 and a metal layer 304formed thereupon. For example, the bonding layer 310 is formed on theupper surface of the fins and the metal layer 304 is formed upon thefront surface of the fins, the rear surface of the fins, a first sidesurface of the fins, and an opposing second side surface of the fins.The metal layer 304 may also be formed upon the lower surface of eachfin trench. Semiconductor microcooler 300C may include a lower surface301, and upper surface 303, a first side surface 305, and a second sidesurface 307. The bonding layer 310 may be a layer of indium, titanium,silicon oxide, or the like.

One or more semiconductor microcooler(s) 300C may be thermally connectedto one or more surfaces of first housing 202 and/or the second housing204 that defines conduit region 212, to increase the surface areathereof. As such, heat from the one or more surfaces of first housing202 and/or the second housing 204 is transferred into the fins 302 andinto the metal layer 304. The semiconductor microcooler(s) 300C may bepositioned such that the fins 302 are generally parallel to thedirection of the liquid coolant flow 210. Generally, when semiconductormicrocooler(s) 300C are thermally connected to the one or more surfacesof first housing 202 and/or the second housing 204, the liquid coolantflows within the fin trenches. In this way, with the addition of the oneor more semiconductor microcooler(s) 300 within the conduit region 212,heat is transferred relatively more efficiently from the first housing202 and/or the second housing 204 into the liquid coolant flow 210.

FIG. 6B depicts a cross section view of a stacked semiconductormicrocooler 300D, according to one or more embodiments of the presentinvention. Stacked semiconductor microcooler 300D includes a pluralityof stacked semiconductor microcoolers 300C. For example, stackedsemiconductor microcooler 300D includes a semiconductor microcooler300C₁ and a semiconductor microcooler 300C₂. Semiconductor microcooler300C₂ is stacked upon semiconductor microcooler 300C₁. For clarity,though two semiconductor microcoolers 300C are shown stacked, a stackedsemiconductor microcooler may include a greater number of semiconductormicrocoolers 300 stacked relative to one another.

The plurality of stacked semiconductor microcooler 300C may have thesame orientation, whereby each lower surface 301 of each semiconductormicrocooler 300C is facing the same direction. In such implementation,the top surface 303 of a semiconductor microcooler 300C may be bondedand thermally connected to the lower surface 301 of anothersemiconductor microcooler 300C. The semiconductor microcooler 300C maybe stacked such that the fins 302 and fin trenches of the semiconductormicrocoolers 300C are aligned. First side surface 325 may be formed bycoplanar first side surfaces 305 of each semiconductor microcooler 300C.Likewise, second side surface 327 may be formed by coplanar second sidesurfaces 307 of each semiconductor microcooler 300C.

Alternatively, the stacked semiconductor microcooler 300C may havediffering orientation whereby lower surfaces 301 of two or moresemiconductor microcooler 300C may face towards each other or away fromeach other. In such implementation, the top surface 303 of asemiconductor microcooler 300C may be bonded and thermally connected tothe top surface 303 of another semiconductor microcooler 300C. The fins302 and fin trenches of these semiconductor microcoolers 300C may bealigned, thereby increasing (e.g. doubling, etc.) the size of the fintrenches that separate the fins 302, as depicted. First side surface 325may be formed by a coplanar first side surface 305 of a firstmicrocooler 300C and a second side surface 307 of a second microcooler300C. Likewise, second side surface 327 may be formed by a coplanarsecond side surface 307 of the first microcooler 300C and the first sidesurface 307 of the second microcooler 300C.

Stacked semiconductor microcooler 300D may include a lower surface 321,an upper surface 323, a first side surface 325, and a second sidesurface 325. Such surfaces 321, 323, 325, and/or 325 may be thermallyconnected to one or more surfaces of first housing 202 and/or the secondhousing 204 that defines conduit region 212, to increase the surfacearea thereof. As such, heat from the one or more surfaces of firsthousing 202 and/or the second housing 204 is transferred into the fins302 and into the metal layer 304. The stacked semiconductormicrocooler(s) 300D may be positioned such that the fins 302 of eachmicrocooler 300 are generally parallel to the direction of the liquidcoolant flow 210. Generally, when stacked semiconductor microcooler(s)300D are thermally connected to the one or more surfaces of firsthousing 202 and/or the second housing 204, the liquid coolant flowswithin the fin trenches. In this way, with the addition of the one ormore stacked semiconductor microcooler(s) 300D within the conduit region212, heat is transferred relatively more efficiently from the firsthousing 202 and/or the second housing 204 into the liquid coolant flow210.

FIG. 7 depicts a cross section view of a stacked semiconductormicrocooler 300E, according to one or more embodiments of the presentinvention. Stacked semiconductor microcooler 300E includes a pluralityof stacked semiconductor microcoolers 300E. For example, stackedsemiconductor microcooler 300E includes a semiconductor microcooler300C₁, a semiconductor microcooler 300C₂′ that has had its backsidepolished, and semiconductor microcooler 300C₃. Semiconductor microcooler300C₂′ is stacked upon semiconductor microcooler 300C₁, Semiconductormicrocooler 300C₃ is stacked upon semiconductor microcooler 300C₂′ Forclarity, though three semiconductor microcoolers 300C are shown stacked,a stacked semiconductor microcooler may include two or moresemiconductor microcoolers 300C stacked relative each other.

The plurality of stacked semiconductor microcooler 300C may have thesame orientation, whereby each lower surface 301 of each semiconductormicrocooler 300C is facing the same direction. In such implementation,the top surface 303 of a semiconductor microcooler 300C may be bondedand thermally connected to the lower surface 301 of anothersemiconductor microcooler 300C. The semiconductor microcoolers 300C maybe stacked such that the fins 302 and fin trenches of the semiconductormicrocoolers 300E are aligned. First side surface 325 may be formed bycoplanar first side surfaces 305 of each semiconductor microcooler 300C.Likewise, second side surface 327 may be formed by coplanar second sidesurfaces 307 of each semiconductor microcooler 300C.

As depicted, the plurality of stacked semiconductor microcooler 300E mayhave differing orientation whereby lower surfaces 301 of thesemiconductor microcoolers 300C may face towards each other and/or awayfrom each other. In such implementation, the top surface 303 of asemiconductor microcooler 300C₁ may be bonded and thermally connected tothe top surface 303 of another semiconductor microcooler 300C₂′. Thebackside of semiconductor microcooler 300C₂′ is polished to removeexcess semiconductor material and/or metal layer 304 material such thatfins 302 and metal layer 304 thereupon remain. Subsequently, the topsurface 303 of semiconductor microcooler 300C₃ may be bonded andthermally connected to the polished backside surface of semiconductormicrocooler 300C₂′.

The fins 302 and fin trenches of these semiconductor microcoolers 300Cmay be aligned, thereby increasing (e.g. tripling, as is depicted, etc.)the size of the fin trenches that separate the fins 302. First sidesurface 325 may be formed by a coplanar first side surface 305 of afirst microcooler 300 and a second side surface 307 of a secondmicrocooler 300. Likewise, second side surface 327 may be formed by acoplanar second side surface 307 of the first microcooler and the firstside surface 307 of the second microcooler 300E.

Stacked semiconductor microcooler 300E may include a lower surface 321,an upper surface 323, a first side surface 325, and a second sidesurface 325. Such surfaces 321, 323, 325, and/or 325 may be thermallyconnected to one or more surfaces of first housing 202 and/or the secondhousing 204 that defines conduit region 212, to increase the surfacearea thereof. As such, heat from the one or more surfaces of firsthousing 202 and/or the second housing 204 is transferred into the fins302 and into the metal layer 304. The stacked semiconductormicrocooler(s) 300E may be positioned such that the fins 302 of eachmicrocooler 300C are generally parallel to the direction of the liquidcoolant flow 210. Generally, when stacked semiconductor microcooler(s)300E are thermally connected to the one or more surfaces of firsthousing 202 and/or the second housing 204, the liquid coolant flowswithin the fin trenches. In this way, with the addition of the one ormore stacked semiconductor microcooler(s) 300E within the conduit region212, heat is transferred relatively more efficiently from the firsthousing 202 and/or the second housing 204 into the liquid coolant flow210.

FIG. 8 depicts an initial fabrication stage of a process flow to form asemiconductor microcooler, according to one or more embodiments of thepresent invention. At the initial fabrication stage, a bulksemiconductor substrate 400 is provided.

The semiconductor substrate 400 is a bulk semiconductor materialsubstrate. Semiconductor substrate materials may include undoped Si, ndoped Si, p doped Si, single crystal Si, polycrystalline Si, amorphousSi, Ge, SiGe, SiC, SiGeC, Ga, GaAs, InAs, InP and all other III/V orII/VI compound semiconductors. In a preferred embodiment, semiconductorsubstrate 400 is a Si bulk substrate. Typically, the substrate 400 maybe about, but is not limited to 700-800 um. For example, the substrate400 may have a thickness ranging from 0.5 mm to about 3 mm.

FIG. 9 depicts another fabrication stage of the process flow to form asemiconductor microcooler, according to one or more embodiments of thepresent invention. At this fabrication stage, a finned semiconductorsubstrate 400′ is formed. Finned semiconductor substrate 400′ is formedby fabricating fins 302 within substrate 400. Finned semiconductorsubstrate 400′ may also include a front surface, rear surface, lowersurface 301, first side surface 305, and second side surface 307. A fin302 may include a front surface, rear surface, first sidewall surface370, second sidewall surface 372, and top surface 309.

Fins 302 may be formed by known fin fabrication techniques such assubtractive removal techniques that remove selective portions ofsubstrate 400 and retain other portions of substrate 400 to thereby formfins 302. For example, a mask may be formed upon the upper surface ofsubstrate 400. The mask may be patterned to expose underlying portionsof substrate 400 while protecting other underlying portions of substrate400. The exposed portions of substrate 400 are removed (e.g., by anetchant, or the like) and the protected portions of substrate 400 areretained and form the fins 302. Subsequently, the mask is removed fromthe fins 302.

FIG. 10 depicts another fabrication stage of the process flow to form asemiconductor microcooler, according to one or more embodiments of thepresent invention. At this fabrication stage, semiconductor microcooler300 is formed. Semiconductor microcooler 300 is formed by forming metallayer 304 upon fins 302. Metal layer 304 may be formed by knownmetallization techniques. For example, metal layer 304 may be formed bydeposition, plating, or the like. Metal layer 304 may be formed upon thefront surface, rear surface, first sidewall surface 370, second sidewallsurface 372, and top surface 309 of fins 302. In some embodiments, asdepicted, metal layer 304 is not formed upon surface 301, 305, and/or307. However, for clarity, metal layer 304 may alternatively be formedupon surface 301, 305, and/or 307 of finned semiconductor substrate400′. In these implementations, surfaces 301, 305, and/or 307 of finnedsemiconductor substrate 400′ are therefore metal.

Metal layer 304 may be a layer of metal formed from a metal or metalcompound, such as a layer of copper, aluminum, tungsten, or like. In apreferred embodiment, metal layer 304 is a Cu metal layer. The thicknessof metal layer 304 may be the same thickness of the associated fin 302.For example, the metal layer 304 may have a thickness ranging from 0.025to 0.1 mm.

Semiconductor microcooler 300 may also include a front surface, rearsurface, lower surface 301, first side surface 305, second side surface307, and upper surface 303.

FIG. 11 depicts another fabrication stage of the process flow to form asemiconductor microcooler, according to one or more embodiments of thepresent invention. At this fabrication stage, semiconductor microcooler402 is formed. Semiconductor microcooler 402 may be formed by removingthe metal layer 304 that is upon the upper surface 309 of each fin 302of semiconductor microcooler 300. The metal layer 304 that is upon theupper surface 309 of each fin 302 may be removed by known substantiveremoval techniques. For example, a chemical mechanical polish (CMP)technique may remove the metal layer 304 that is upon the upper surface309 of each fin 302. Generally, the metal layer 304 that is within thefin trenches of semiconductor microcooler 402 (i.e. upon the firstsidewall surface 370, upon the second sidewall surface 372, and upon thelower surface of the fin trench) may be retained while the metal layer304 locally upon the upper surface 309 of fins 302 is removed therebyexposing the upper surface 309 of fins 302.

FIG. 12 depicts another fabrication stage of the process flow to form asemiconductor microcooler, according to one or more embodiments of thepresent invention. At this fabrication stage, semiconductor microcooler300C is formed. Semiconductor microcooler 300C may be formed by formingbonding layer 310 upon the exposed upper surface 309 of fins 302 ofsemiconductor microcooler 402. As depicted, bonding layer 310 may alsobe formed upon the upper surfaces of metal layer 304 of semiconductormicrocooler 402.

In some implementations bonding layer 310 may be formed locally to theexposed upper surface 309 of fins 302 and/or upon the upper surfaces ofmetal layer 304 that are substantially coplanar (i.e. such surfaces arecoplanar within an appropriate fabrication tolerance) with the uppersurface 309 of the associated fin 302. In other implementations, ablanket bonding layer may be formed upon the exposed upper surface 309of fins 302 and upon the metal layer 304. Subsequently, portions of theblanket bonding layer within the fin trenches are removed and theportions of the blanket bonding layer 304 upon the upper surface 309 offins 302 and/or upon the upper surfaces of metal layer 304 that aresubstantially coplanar with the upper surface 309 of the associated fin302 are retained as bonding layer 310.

Bonding layer 310 may be a layer of Indium, Tungsten, Titanium, SiliconOxide, or the like. In a preferred embodiment, bonding layer is anIndium layer. Generally bonding layer 310 is formed of a material thathas greater adherence relative to the material of fins 302. As such,semiconductor microcooler 300C that includes bonding layer 310 may beutilized in implementations where a stacked semiconductor microcooler isfabricated where the bonding layer 310 bonds the individualsemiconductor microcoolers.

In some embodiments, the thickness of bonding layer 310 is the same asthe thickness of the metal layer 304. Bonding layer 310 may be about,but is not limited to, 0.050 mm. For example, the bonding layer 310 mayhave a thickness ranging from 0.0255 mm to about 0.15 mm.

Semiconductor microcooler 300C may also include a front surface, rearsurface, lower surface 301, first side surface 305, second side surface307, and upper surface 303.

FIG. 13 depicts another fabrication stage of the process flow to form asemiconductor microcooler, according to one or more embodiments of thepresent invention. At this fabrication stage, semiconductor microcooler404 is formed. Semiconductor microcooler 404 includes a filler 410within each fin trench. Semiconductor microcooler 404 may be formed byforming filler 410 within the fin trenches of semiconductor microcooler402. Filler 410 is a metal with a melting point above ambient and lowerto the melting point of the metal of metal layer 304. Filler 410 maygenerally provide mechanical support, structural stability, rigidity, orthe like when formed within the fin trenches.

Filler 410 may be formed by known fabrication techniques such asdeposition, plating, or the like. In one implementation, a filler 410 isformed upon the metal layer 304 within and filling the fin trenches. Inanother implementation, a blanket filler layer is formed upon the metallayer 304 and upon the fins 302. Excess blanket filler layer may beremoved with a polishing technique, e.g., a CMP that stops at surface309 of the fins 302. Residual blanket filler layer material ismaintained within the fin trenches, thereby forming fillers 410.

The upper surface of each filler 410 may be substantially coplanar withthe upper surface 309 of the fins 302.

FIG. 14 depicts another fabrication stage of the process flow to form asemiconductor microcooler, according to one or more embodiments of thepresent invention. At the present fabrication stage, stackedsemiconductor microcooler 412 is formed by connecting two or moresemiconductor microcoolers 404.

Stacked semiconductor microcooler 412 includes a plurality of stackedsemiconductor microcoolers 404. For example, stacked semiconductormicrocooler 412 includes a semiconductor microcooler 404 ₁,semiconductor microcooler 404 ₂, and semiconductor microcooler 404 ₃.Semiconductor microcooler 404 ₂ is stacked upon semiconductormicrocooler 404 ₁. Semiconductor microcooler 404 ₃ is stacked uponsemiconductor microcooler 404 ₂. For clarity, though three semiconductormicrocoolers 404 are shown stacked, stacked semiconductor microcooler412 may include two or more semiconductor microcoolers 404 stackedrelative each other.

The plurality of stacked semiconductor microcooler 404 may have the sameorientation, as is depicted, whereby each lower surface 301 of eachsemiconductor microcooler 404 is facing the same direction. In suchimplementation, the top surface of a semiconductor microcooler 404 maybe bonded and thermally connected to the lower surface 301 of anothersemiconductor microcooler 404. The semiconductor microcooler 404 may bestacked such that the fins 302, fin trenches, and fillers 410 of thesemiconductor microcoolers 404 are vertically aligned. First sidesurface 325 may be formed by coplanar first side surfaces 305 of eachsemiconductor microcooler 404. Likewise, second side surface 327 may beformed by coplanar second side surfaces 307 of each semiconductormicrocooler 404.

Stacked semiconductor microcooler 300B, as is shown in FIG. 5, may beformed by heating stacked semiconductor microcooler 404 to a temperatureabove the melting point of fillers 410 such that the material of fillers410 is flows (i.e., into and out of the page) out of the fin trenches.Thus, after the removal of fillers 410, the fin trenches of stackedsemiconductor microcooler 300B are open or void of substantial blockagesthat would prevent liquid coolant to flow 210 therethrough.

FIG. 15 depicts another fabrication stage of the process flow to form asemiconductor microcooler, according to one or more embodiments of thepresent invention. At the present fabrication stage, stackedsemiconductor microcooler 413 is formed by connecting semiconductormicrocooler 404 ₁ and semiconductor microcooler 404 ₂.

Semiconductor microcooler 404 ₁ and semiconductor microcooler 404 ₂ havea different orientation whereby lower surfaces 301 of semiconductormicrocooler 404 ₁ and semiconductor microcooler 404 ₂ face away fromeach other. In such implementation, the top surface 303 of semiconductormicrocooler 404 ₁ is be bonded and thermally connected to the topsurface 303 of semiconductor microcooler 404 ₂. The fins 302, fintrenches, and fillers 410 of semiconductor microcooler 404 ₁ andsemiconductor microcooler 404 ₂ are vertically aligned, therebyincreasing (e.g. doubling, etc.) the size of the fin trenches thatseparate the fins 302. First side surface 325 may be formed by acoplanar first side surface 305 of semiconductor microcooler 404 ₁ andsecond side surface 307 of semiconductor microcooler 404 ₂. Likewise,second side surface 327 may be formed by a coplanar second side surface307 of the semiconductor microcooler 404 ₁ and the first side surface307 of the semiconductor microcooler 404 ₂.

A stacked semiconductor microcooler 413′ may be formed by heatingstacked semiconductor microcooler 413 to a temperature above the meltingpoint of fillers 410 such that the material of fillers 410 flows (i.e.,into and out of the page) out of the fin trenches. Thus, after theremoval of fillers 410, the fin trenches of stacked semiconductormicrocooler 413′ are open or void of substantial blockages that wouldprevent liquid coolant to flow 210 therethrough. The stackedsemiconductor microcooler 413′ may be thermally connected to one or moresurfaces within conduit region 212, as described with reference to theother semiconductor microcoolers depicted herein. Stacked semiconductormicrocooler 413′ may be depicted as stacked semiconductor microcooler413, shown in FIG. 15, without fillers 410 within the fin trenches.

FIG. 16 depicts another fabrication stage of the process flow to form asemiconductor microcooler, according to one or more embodiments of thepresent invention. At the present fabrication stage, stackedsemiconductor microcooler 414 is formed by polishing the backside ofsemiconductor microcooler 404 ₂ thereby forming polished semiconductormicrocooler 404 ₂′.

The backside of semiconductor microcooler 404 ₂ may be polished with aCMP technique that removes the backside of semiconductor microcooler 404₂ to a surface 416 that is coplanar with the backside surface of filler410. In other words, the semiconductor bulk substrate 400 material andthe metal layer 310 material on the backside of semiconductormicrocooler 404 ₂ is polished away until the fillers 410 within the fintrenches are exposed.

FIG. 17 depicts another fabrication stage of the process flow to form asemiconductor microcooler, according to one or more embodiments of thepresent invention. At the present fabrication stage, stackedsemiconductor microcooler 416 is formed by connecting semiconductormicrocooler 4043 and stacked semiconductor microcooler 414.

The polished backside surface of semiconductor microcooler 404 ₂ isbonded and thermally connected to the top surface 303 of semiconductormicrocooler 404 ₃. The fins 302, fin trenches, and fillers 410 ofsemiconductor microcooler 404 ₃ and such features of stackedsemiconductor microcooler 414 are vertically aligned, thereby increasing(e.g. tripling, etc.) the size of the fin trenches that separate thefins 302. First side surface 325 may be formed by coplanar side surfacesand second side surface 327 may be formed by coplanar side surfaces.

Stacked semiconductor microcooler 300E, as depicted in FIG. 7, may beformed by heating stacked semiconductor microcooler 416 to a temperatureabove the melting point of fillers 410 such that the material of fillers410 flows (i.e., into and out of the page) out of the fin trenches.Thus, after the removal of fillers 410, the fin trenches of stackedsemiconductor microcooler 300E are open or void of substantial blockagesthat would prevent liquid coolant to flow 210 therethrough.

FIG. 18 depicts an electronic system 500 comprising an IC chip 102 thatis cooled by a liquid cooling system that utilizes one or moreembodiments of the present invention. Electronic system 500 may be forexample a computer, kiosk, server, mobile device, tablet, and the like.System 500 includes liquid cooled package 200. To assist in the removalof heat from chip 102, package 200 is thermally connected to chip 102via thermal interface material 112. As such, heat generated from theoperation of IC chip 102 is transferred into first housing 202 and thesecond housing 204.

One or more semiconductor microcoolers (e.g., 300 ₁, 300 ₂, and 300 ₃)are thermally connected to one or more surfaces of first housing 202and/or the second housing 204 that defines conduit region 212, withinthe cavity 205, to increase the surface area thereof. For example,surface 301 of each of the one or more semiconductor microcoolers isthermally connected to surface 203 of the first housing 202. In oneembodiment, one or more microcooler is thermally connected to the bottomsurface and applicable side surfaces of the one or more microcooler(s)nearest the side surfaces of the cavity 205 are within a fin width fromsuch surfaces and each of the upper surfaces of the microcooler(s) arewithin a layer 304 thickness from the upper surface of cavity 205. Forexample, the left side surface of microcooler 300 is within a fin widthof the left side surface of cavity 205, the right side surface ofmicrocooler 300 is within a fin width of the right side surface ofcavity 205, and the upper surface of microcooler 300 is within a layer304 thickness from the upper surface of cavity 205.

Heat from the one or more surfaces of the first housing 202 and/or thesecond housing 204 is transferred into the fins 302 and into the metallayer 304 of semiconductor microcooler(s). The semiconductormicrocooler(s) may be positioned such that the fins 302 are generallyparallel to the direction of the liquid coolant flow 210 to promoteliquid coolant flowing through the fin trenches. Generally, whensemiconductor microcooler(s) are thermally connected to the one or moresurfaces of first housing 202 and/or the second housing 204, the liquidcoolant flows within the fin trenches. In this way, with the addition ofthe one or more semiconductor microcoolers within the conduit region212, heat is transferred relatively more efficiently from the firsthousing 202 and/or the second housing 204 into the liquid coolant flow210.

FIG. 19 depicts an electronic system 500 comprising an IC chip 102 thatis cooled by a liquid cooling system that utilizes one or moreembodiments of the present invention. In the depicted example, one ormore semiconductor microcoolers (e.g., 300E₁, 300E₂, and 300E₃) arethermally connected to one or more surfaces of first housing 202 and/orthe second housing 204 that defines conduit region 212, within thecavity 205, to increase the surface area thereof. For example, surface321 of each of the semiconductor microcooler(s) is thermally connectedto surface 203 of the first housing 202. In one embodiment, one or moremicrocooler is thermally connected to the bottom surface and applicableside surfaces of the one or more microcooler(s) nearest the sidesurfaces of the cavity 205 are within a fin width from such surfaces andeach of the upper surfaces of the microcooler(s) are within a layer 304thickness from the upper surface of cavity 205. For example, the leftside surface of the microcooler 300E₁ is within a fin width of the leftside surface of cavity 205, the right side surface of microcooler 300E₂is within a fin width of the right side surface of cavity 205, and theupper surface of microcooler 300E₁ and 300 ₂ is within a layer 304thickness from the upper surface of cavity 205.

Heat from the one or more surfaces of the first housing 202 and/or thesecond housing 204 is transferred into the fins 302 and into the metallayer 304 of semiconductor microcooler(s). The semiconductormicrocooler(s) may be positioned such that the fins 302 are generallyparallel to the direction of the liquid coolant flow 210 to promoteliquid coolant flowing through the fin trenches. Generally, whensemiconductor microcooler(s) are thermally connected to the one or moresurfaces of first housing 202 and/or the second housing 204, the liquidcoolant flows within the fin trenches. In this way, with the addition ofthe one or more semiconductor microcooler(s) within conduit region 212,heat is transferred relatively more efficiently from the first housing202 and/or the second housing 204 into the liquid coolant flow 210.

For clarity, though semiconductor microcoolers 300 and semiconductormicrocoolers 300E₁ and 300E₂ are depicted within an electronic system500 in FIGS. 18 and 19, respectively, other semiconductor microcoolers(or any combination thereof) may so be included therein. For example,semiconductor microcoolers 300B, 300C, 300D, 402, 413′, or the like maybe thermally connected to one or more surfaces of first housing 202and/or the second housing 204 that defines conduit region 212, withinthe cavity 205, to increase the surface area thereof to more efficientlytransfer heat into the liquid coolant flow 210.

Further, for clarity, though a semiconductor microcooler may be depictedin a Figure without an element compared to another semiconductormicrocooler depicted in a different Figure, the former semiconductormicrocooler may include such feature. For example, semiconductormicrocoolers 404 ₁, 404 ₂, and/or 404 ₃ depicted in FIG. 17 may includebonding layer 310, though bonding layer 310 is not depicted in FIG. 17.

FIG. 20 depicts a method 600 for fabricating a semiconductormicrocooler, according to one or more embodiments of the presentinvention. Method 600 begins at block 602 and continues with forming afirst finned semiconductor substrate that includes at least a pluralityof fins and a metal layer upon the fins (block 604). For example, fins302 are formed in a first bulk semiconductor substrate 400 and metallayer 304 is formed upon the fins 302 to form a first semiconductormicrocooler 3001, or in other words, to form a first finnedsemiconductor substrate that includes at least a plurality of fins and ametal layer upon the fins.

Method 600 may continue with forming a second finned semiconductorsubstrate that includes at least a plurality of fins and a metal layerupon the fins (block 606). For example, fins 302 are formed in a secondbulk semiconductor substrate 400 and metal layer 304 is formed upon thefins 302 to form a second semiconductor microcooler 300 ₂, or in otherwords, to form a second finned semiconductor substrate that includes atleast a plurality of fins and a metal layer upon the fins.

Method 600 may continue with removing the metal layer upon the uppersurface of the fins of the first finned semiconductor substrate (block608). For example, the metal layer 304 locally upon the upper surface309 of the fins 302 of semiconductor microcooler 300 ₁ are removed toexpose upper surface 309 of the fins 302 of semiconductor microcooler300 ₁ while the metal layer 304 on the one or more side surfaces of thefins 302 remain.

Method 600 may continue with forming a bonding layer upon the uppersurface of the fins of the first finned semiconductor substrate (block610). For example, bonding layer 310 is formed locally upon the uppersurface 309 of the fins 302 of semiconductor microcooler 300 ₁ and uponthe upper surfaces of the metal layer 304 that is on the one or moreside surfaces of the fins 302 to form semiconductor microcooler 300C₁.

Method 600 may continue with stacking the first finned semiconductorsubstrate and the second finned semiconductor substrate (block 612). Forexample, semiconductor microcooler 300C₁ is bonded and thermallyconnected to semiconductor microcooler 300 ₂ via the bonding layer 310that is upon the upper surface 309 of the fins 302 of semiconductormicrocooler 300 ₁. Method 600 ends at block 614.

FIG. 21 depicts a method 630 for fabricating a semiconductormicrocooler, according to one or more embodiments of the presentinvention. Method 630 begins at block 632 and continues with forming afirst finned semiconductor substrate that includes at least a pluralityof fins and a metal layer upon the fins (block 634). For example, fins302 are formed in a first bulk semiconductor substrate 400 and metallayer 304 is formed upon the fins 302 to form a first semiconductormicrocooler 300 ₁, or in other words, to form a first finnedsemiconductor substrate that includes at least a plurality of fins and ametal layer upon the fins.

Method 630 may continue with forming a second finned semiconductorsubstrate that includes at least a plurality of fins and a metal layerupon the fins (block 636). For example, fins 302 are formed in a secondbulk semiconductor substrate 400 and metal layer 304 is formed upon thefins 302 to form a second semiconductor microcooler 300 ₂, or in otherwords, to form a second finned semiconductor substrate that includes atleast a plurality of fins and a metal layer upon the fins.

Method 630 may continue with removing the metal layer upon the uppersurface of the fins of the first finned semiconductor substrate (block638). For example, the metal layer 304 locally upon the upper surface309 of the fins 302 of semiconductor microcooler 300 ₁ are removed toexpose upper surface 309 of the fins 302 of semiconductor microcooler300 ₁ while the metal layer 304 on the one or more side surfaces of thefins 302 remain.

Method 630 may continue with forming a bonding layer upon the uppersurface of the fins of the first finned semiconductor substrate and uponthe fins of the second finned semiconductor substrate (block 640). Forexample, a first bonding layer 310 is formed locally upon the uppersurface 309 of the fins 302 of semiconductor microcooler 300 ₁ and uponthe upper surfaces of the metal layer 304 that is on the one or moreside surfaces of the fins 302 to form semiconductor microcooler 300C₁and a second bonding layer 310 is formed locally upon the upper surface309 of the fins 302 of semiconductor microcooler 3002 and upon the uppersurfaces of the metal layer 304 that is on the one or more side surfacesof the fins 302 to form semiconductor microcooler 300C₂.

Method 630 may continue with forming a filler within each fin trenchthat separates the neighboring fins of the fins of the first finnedsemiconductor substrate and within each fin trench that separates theneighboring fins of the fins of the second finned semiconductorsubstrate (block 642). For example, a filler 410 is formed within uponthe metal layer 304 upon the sidewalls of fins 302 of semiconductormicrocooler 300 ₁ within the fin trench that separates neighboring fins302. Likewise, a filler 410 is formed within upon the metal layer 304upon the sidewalls of fins 302 of semiconductor microcooler 300 ₂ withinthe fin trench that separates neighboring fins 302.

Method 630 may continue with stacking the first finned semiconductorsubstrate and the second finned semiconductor substrate (block 644). Forexample, stacked semiconductor microcooler 413 may be formed by stackingthe semiconductor microcooler 300 ₂ upon semiconductor microcooler 300₁.

Method 630 may continue with polishing the backside of the second finnedsemiconductor substrate (block 644). For example, the backside ofsemiconductor microcooler 300 ₂ is polished to expose the fillers 410that separate the neighboring fins 302 of the semiconductor microcooler3002.

Method 630 may continue with forming a third finned semiconductorsubstrate that includes at least a plurality of fins and a metal layerupon the fins (block 648). For example, fins 302 are formed in a thirdbulk semiconductor substrate 400 and metal layer 304 is formed upon thefins 302 to form a third semiconductor microcooler 300 ₃, or in otherwords, to form a third finned semiconductor substrate that includes atleast a plurality of fins and a metal layer upon the fins.

Method 630 may continue with stacking the third finned semiconductorsubstrate to the polished backside of the second finned semiconductorsubstrate (block 650). For example, third semiconductor microcooler 300₃ is stacked upon the polished backside of the semiconductor microcooler300 ₂ to form stacked semiconductor microcooler 416.

Method 630 may continue with removing the fillers within each fin trenchthat separates the neighboring fins (block 652). For example, fillers410 are removed from the fin trenches of semiconductor microcoolers 300₁, 300 ₂, and 300 ₃. Method 630 ends at block 654.

FIG. 22, FIG. 23, and FIG. 24 depict a stacked semiconductor microcooler700, according to one or more embodiments of the present invention.Stacked semiconductor microcooler 700, as depicted, includes stackedsemiconductor microcooler 300B which includes microcooler 300 ₁,microcooler 300 ₂, and microcooler 3003, though stacked microcooler 700may include other microcooler arrangements, such as stackedsemiconductor microcooler 300E, or the like.

Stacked semiconductor microcooler 700 includes inlet/outlet passages 702through the stacked semiconductor microcooler 700. Inlet/outlet passages702 may be referred herein as access passage(s). For example,inlet/outlet passages 702 may extend from the surface 309 of microcooler300 ₃, as depicted in FIG. 24, to bottom of the fin trench ofmicrocooler 300 ₁. One of the inlet/outlet passages 702 may beconfigured as an inlet where liquid coolant may be introduced intostacked semiconductor microcooler 700. One of the inlet/outlet passages702 may be configured as an outlet where liquid coolant may be expelledfrom stacked semiconductor microcooler 700. In some embodiments theremay be multiple inlet passages and multiple outlet passages withinstacked semiconductor microcooler 700.

Access passage(s) may be formed within each microcooler prior tostacking such microcoolers by removing a portion of one or more fins andone or more portions of the bulk substrate adjacent to the fin(s). Insuch embodiment, the microcoolers may be positioned with respect theretoto align the access passages. Access passage(s) may be formed withineach microcooler after stacking such microcoolers by removing alignedportions of respective one or more fins and aligned portions of therespective bulk substrates adjacent to the associated fin(s).

Inlet/outlet passages 702 generally allows flow access to each level ofthe stacked semiconductor microcooler 700. For example, inlet passage702 allows for coolant to pass through semiconductor microcooler 303 ₃to the underlying semiconductor microcooler 303 ₂. Likewise inletpassage 702 allows for coolant to pass through semiconductor microcooler303 ₂ to the underlying semiconductor microcooler 303 ₁. In this manner,inlet passage 702 allows for coolant to flow to and through each levelof the stacked semiconductor microcooler 700. Similarly, outlet passage702 allows for coolant exiting semiconductor microcooler 303 ₂ to passthrough the above semiconductor microcooler 303 ₃. Likewise outletpassage 702 allows for coolant exiting semiconductor microcooler 303 ₁to pass through both the above semiconductor microcoolers 3032 and 303₃. In this manner, outlet passage 702 allows for coolant to flow out ofeach level of the stacked semiconductor microcooler 700.

FIG. 25 and FIG. 26 depicts stacked semiconductor microcooler assembly750, according to one or more embodiments of the present invention.Stacked semiconductor microcooler assembly 750 includes stackedsemiconductor microcooler 700 and frame 754. Stacked semiconductormicrocooler assembly 750 may also include a liner 752 between thestacked semiconductor microcooler 700 and frame 754. Generally, stackedsemiconductor microcooler 700 is configured to fit within frame 754 suchthat one or more sidewalls (i.e., front, rear, left, right, and thelike) of stacked semiconductor microcooler 700 contacts an innerrespective sidewall of the frame 754. Frame 754 may be fabricated frommetal, plastic, or the like. Liner 752 may be fabricated from a rubberor other such compliant material and may be, for example, a viton pad.Frame 754 is generally open on one side such a semiconductor microcooler700 surface is exposed such that it may be directly connected to anintegrated circuit chip. For example, as depicted, frame 754 and stackedsemiconductor microcooler 700 are positioned together such that surface301 of microcooler 300 ₁ is exposed such that it may be directlyconnected to an integrated circuit chip.

Frame 754 includes an inlet/outlet 756 generally aligned withinlet/outlet passages 702. One of the inlet/outlet 756 may be configuredas an inlet where liquid coolant may be introduced into stackedsemiconductor microcooler 700 through frame 754. One of the inlet/outlet756 may be configured as an outlet where liquid coolant may be expelledfrom stacked semiconductor microcooler 700 through frame 754. In someembodiments there may be multiple inlets and multiple outlets withinframe 754 each associated with a respective inlet or outlet passage ofstacked semiconductor microcooler 700. Frame 756 may also include aflange 758 that is configured to connect with a liquid coolant conduit.

FIG. 27 depicts an electronic system 800 comprising an IC chip 102 thatis cooled by a liquid cooling system that utilizes one or moreembodiments of the present invention. Electronic system 800 may be forexample a computer, kiosk, server, mobile device, tablet, and the like.System 800 includes stacked semiconductor microcooler assembly 750. Toassist in the removal of heat from chip 102, the exposed surface ofstacked semiconductor microcooler 700 is thermally connected to chip 102via thermal interface material 112. As such, heat generated from theoperation of IC chip 102 is transferred into stacked semiconductormicrocooler 700.

Heat from the one or more surfaces of the semiconductor microcoolers 300₁, 300 ₂, and 300 ₃ of stacked semiconductor microcooler 700 istransferred into the fins 302 and into the metal layer 304. Thesemiconductor microcoolers 300 ₁, 300 ₂, and 300 ₃ may be positionedsuch that the fins 302 are generally parallel to the direction of theliquid coolant flow 210 to promote liquid coolant flowing through thefin trenches. Generally, when semiconductor microcoolers 300 ₁, 300 ₂,and 300 ₃ are thermally connected to the one or more surfaces of firsthousing 202 and/or the second housing 204, the liquid coolant flowswithin the fin trenches. In this way, with the addition of the one ormore semiconductor microcoolers 300 ₁, 300 ₂, and 300 ₃, heat istransferred relatively more efficiently from the first housing 202and/or the second housing 204 into the liquid coolant flow 210.

Liquid coolant flow 210 may be induced by a cooled coolant enteringstacked semiconductor microcooler 700 from within hose 806. Hose 806 maybe attached to flange 758 by fitting 804. The cooled coolant entersstacked semiconductor microcooler 700 by way of inlet 756 that isaligned with inlet passage 702. Passage 702 allows the cooled coolant toenter each level of the stacked semiconductor microcooler 700 and passthrough the fin treches thereof, thereby allowing for heat to transferfrom the fins of each level of the stacked semiconductor microcooler 700into the coolant. The heated coolant exits the fin trenches at outletpassage 702 and exits the stacked semiconductor microcooler 700 atoutlet 756 that is aligned with outlet passage 702. The heated coolantenters the hose 808 which may be attached to flange 758 by fitting 804.Hose 808 is configured to route the heated coolant to a coolant chillerthat cools the heated coolant. From the chiller, the coolant may returnto stacked semiconductor microcooler 700 by way of hose 806.

In some embodiments, electronic system 800 may include a frame 802 thatis configured to connect with carrier 108 and frame 754. Frame 802 maygive the carrier 108 rigidity and may force stacked semiconductormicrocooler assembly 750 onto chip 102 such that the exposed surface ofstacked semiconductor microcooler 700 maintains a sufficient forceagainst chip 102 to allow for sufficient heat to transfer from chip 102to stacked semiconductor microcooler 700.

The accompanying figures and this description depicted and describedembodiments of the present invention, and features and componentsthereof. Those skilled in the art will appreciate that any particularprogram nomenclature used in this description was merely forconvenience, and thus the invention should not be limited to use solelyin any specific application identified and/or implied by suchnomenclature.

The descriptions of the various embodiments of the present inventionhave been presented for purposes of illustration, but are not intendedto be exhaustive or limited to the embodiments disclosed. Manymodifications and variations will be apparent to those of ordinary skillin the art without departing from the scope and spirit of the describedembodiments. For example, the order of the fabrication stages listed indepicted blocks may occur out of turn relative to the order indicated inthe Figures, may be repeated, and/or may be omitted partially orentirely. The terminology used herein was chosen to best explain theprinciples of the embodiment, the practical application or technicalimprovement over technologies found in the marketplace, or to enableothers of ordinary skill in the art to understand the embodimentsdisclosed herein.

References herein to terms such as “vertical”, “horizontal”, and thelike, are made by way of example, and not by way of limitation, toestablish a frame of reference. The term “horizontal” as used herein isdefined as a plane parallel to the conventional plane or surface of thecarrier 206, regardless of the actual spatial orientation of the carrier206. The term “vertical” refers to a direction perpendicular to thehorizontal, as just defined. Terms, such as “on”, “above”, “below”,“side” (as in “sidewall”), “higher”, “lower”, “over”, “top”, “under”,“beneath”, and the like, are defined with respect to the horizontalplane. It is understood that various other frames of reference may beemployed for describing the present invention without departing from thespirit and scope of the present invention.

1. A method comprising: forming a first semiconductor microcooler byremoving portions of a first bulk silicon substrate to form a pluralityof first silicon fins and a plurality of first fin trenches, whereineach first fin trench separates adjacent first silicon fins, forming afirst copper layer upon sidewalls of each of the plurality of firstsilicon fins, by forming a first bonding layer upon a respective uppersurface of each of the first plurality of silicon fins, by forming afirst access passage within the first semiconductor microcooler byremoving a portion of a first silicon fin and a portion of the bulksilicon substrate adjacent to the portion of the first silicon fin, andforming a first fin trench filler within each of the plurality of firstfin trenches and within the first access passage; forming a secondsemiconductor microcooler by removing portions of a second bulk siliconsubstrate to form a plurality of second silicon fins and a plurality ofsecond fin trenches, wherein each second fin trench separates adjacentsecond silicon fins, forming a second copper layer upon sidewalls ofeach of the plurality of second silicon fins, by forming a secondbonding layer upon a respective upper surface of each of the secondplurality of silicon fins, forming a second fin trench filler withineach of the plurality of second fin trenches; stacking the firstmicrocooler and the second microcooler by vertically aligning theplurality of first fin trenches with the plurality of second fintrenches and connecting the first bonding layer and the second bondinglayer; and removing the first fin trench filler and the second fintrench filler; wherein the first access passage allows coolant withinone or more first fin trenches to pass through the first semiconductormicrocooler to one or more second fin trenches of the secondsemiconductor microcooler.
 2. (canceled)
 3. The method of claim 1,further comprising: polishing a backside of the second semiconductormicrocooler to expose each of the plurality of second fin trench fillersand to expose each of the plurality of second silicon fins.
 4. Themethod of claim 3, further comprising: forming a second access passagewithin the second semiconductor microcooler by removing a portion of asecond silicon fin and a portion of the bulk silicon substrate adjacentto the portion of the second silicon fin; forming a third semiconductormicrocooler by removing portions of a third bulk silicon substrate toform a plurality of third silicon fins and a plurality of third fintrenches, wherein each third fin trench separates adjacent third siliconfins, forming a third copper layer upon sidewalls of each of theplurality of third silicon fins, by forming a third bonding layer upon arespective upper surface of each of the third plurality of silicon fins,and forming a third fin trench filler within each of the plurality offirst fin trenches; wherein the second access passage allows coolantwithin one or more second fin trenches to pass through the secondsemiconductor microcooler to one or more third fin trenches of the thirdsemiconductor microcooler.
 5. The method of claim 4, further comprising:stacking the third microcooler and the second microcooler by verticallyaligning the plurality of third fin trenches with the exposed pluralityof second fin trenches and thermally connecting the third bonding layerand the exposed plurality of second silicon fins.
 6. The method of claim5, further comprising: removing the third trench filler.
 7. The methodof claim 6, wherein the first fin trench filler, the second fin trenchfiller, and the third trench filler are comprised of a metal that has amelting point above ambient and below that of copper. 8-20. (canceled)